Manav Bhatia <[email protected]> writes: > Hi, > > I am writing to seek some advice about use of iterative solvers > with h-refinement. > > My application is a GLS solver for compressible Euler equations, > and I am running 2D and 3D simulations at transonic Mach > numbers. The initial mesh in 3D analysis has ~2millions tetrahedra, > and the h-refinement process increases this to ~8million > tetrahedra. I am using the standard PETSc GMRES solver with block > Jacobi preconditioner (the default).
Are these steady-state computations or finite time step? > So, a few questions: > -- I am curious about the experience that others have with such > applications? > -- What is the typical Krylov subspace dimension size that people use for > such problems? > -- Are there other built-in preconditioners in PETSc that could do a > better job? Try increasing the overlap slightly '-pc_type asm -pc_asm_overlap 1' (and 2). Perhaps also combine with '-sub_pc_factor_levels 1' (and 2). Let us know if these make a useful difference. It's usually preferable to order your unknowns so that the fields are interlaced, with all values at a node contiguous. > -- Are other custom preconditioners expected to perform better? If so, > which ones? It's hard to beat nonlinear multigrid (FAS) for steady-state problems of this variety, but those depend on having an accurate coarse grid discretization. The favorite for that has always been to use cell-centered (finite volume) discretizations and use agglomeration to produce a coarse operator. A nonlinear relaxation process is of less value for finite element methods because it's relatively more expensive than with FV/FD discretizations. Field-split preconditioners can also be useful, but most will only work properly for low Mach. ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
